Hydraulic circuit for actuation of an earthmoving scraper ejector



Jan. 4, 1966 J, E N ET AL 3,227,050

HYDRAULIC CIRCUIT FOR ACTUATION OF AN EARTHMOVING SCRAPER EJECTOROriginal Filed March 15, 1962 4 Sheets-Sheet 1 INVENTORS. ALLYN J. Hem

BYJOHN A. JuNcK AT T ORNEYS Jan. 4, 1966 A. J. HEIN ET AL 3,227,050

HYDRAULIC CIRCUIT FOR AOTUATION OF AN EARTHMOVING SCRAPER EJ'ECTOROriginal Filed March 15, 1962 4 Sheets-Sheet 2 RESERVOIR EJECTOR APRON'5 P2 INVENTORS.

ALLYN J, Hznu BY JOHN A. J'uNcK A J W 7 ATT ORNEYS Jan. 4, 1966 A. J.HEIN ETAL HYDRAULIC CIRCUIT FOR ACTUATION OF AN EARTHMOVING SCRAPEREJECTOR Original Filed March 15, 1962 4 Sheets-Sheet 5 llu unralhll Q5mm m INVENTORS. ALLYN J. Ham JOHN A. JUNC-K BY ATTORNEYS Jan. 4, 1966 A.J. HEIN ET AL HYDRAULIC CIRCUIT FOR ACTUATION OF AN EARTHMOVING SCRAPEREJECTOR Original Filed March 15, 1962 4 Sheets-Sheet 4 INVENTORS. ALLYNJ'. Ham BYJOHN A. JuNcK z m J ATTORNEYS 3 227,050 HYDRAULIC ClRtIUiT FURAQTUATION OF AN EARTHMQVING SQRAFER EJECTGR Allyn J. Hein and John A.lunch, Juliet, Ill., assignors to Caterpillar Tractor (10., Peoria,111., a corporation of California Uriginal application Mar. 15, 1962,Ser. No. 182,154, new Patent No. 3,138,884, dated June 30, 1964. Dividedand this application Aug. 21, 1963, Ser. No. 303,667

1 flaim. (Cl. 91-436) The present application is a division of ourco-pending application Serial No. 182,154, now Patent No. 3,138,884.

The invention relates to earthmoving scrapers of the kind in whichvarious adjustable elements of the scraper are actuated hydraulically,usually by means of double acting hydraulic jacks and pertainsparticularly to the hydraulic circuit which controls the operation ofthe ejector of the scraper.

The hydraulic circuit claimed herein is disclosed in its use with theejector of an earthmoving scraper but its applicability to othermechanisms will be apparent.

In many large scrapers earth is ejected from the scraper bowl forwardlythrough its open front and by an ejector which normally closes the rearend of the bowl but is mounted for forward ejecting movement underinfluence of a hydraulic jack. Since scraper bowls have a capacity ofmany tons of earth considerable force is required to effect suchejecting action. Heavy sticky types of earth such as clay requiregreater force for ejection than light, dry or granular materials and itsis therefore desirable that the lighter materials be ejected at agreater speed than the heavy materials utilizing the power available andincreasing the overall speed and efficiency of an earthmoving operation.It is also desirable that a two-speed operation of an ejector be madeautomatically responsive to the force or inertia which opposes ejection.This enables a two-speed ejector to start against a heavy load in a lowspeed high force condition and change to a higher speed as the inertiaof the load is overcome and as the weight of the load is reduced afterpartial ejection.

Many ejector circuits are controlled by a sliding spool type hydraulicvalve movable in opposite directions from a central neutral position toan ejecting position and a return position. Resilient centering meansnormally holds the valve in neutral and it must be manually held in itsother positions. It is desirable that the ejector control valve beautomatically maintained in its return position until full return of theejector has been accomplished to free the hands of the operator who isoccupied in steering and actuating other controls as in returning from afill area to perform another loading cycle.

It is therefore the object of the present invention to provide ahydraulic circuit and controls for a scraper ejector which include theabove mentioned desirable features and which is positive and efiicientin operation.

Further and more specific objects and advantages of the invention andthe manner in which it is carried into practice are made apparent in thefollowing specification by reference to the accompanying drawings.

In the drawings:

FIG. 1 is a view in side eelvation of a tractor trailer combinationillustrating the location of the components of the hydraulic circuit ofthe present invention;

FIG. 2 is a schematic view of the entire hydraulic circuit illustratinga two-speed valve in association with the ejector portion of thecircuit;

FIG. 3 is a schematic view illustrating portions of the ejector circuitonly and showing a modified form of twospeed valve in which actuation ofthe valve is automatically controlled;

FIG. 4 is an enlarged fragmentary detail of a portion 3,227,958 PatentedJan. 4, 1866 of a control valve associated with the ejector circuitincluding means employed for holding the control valve in its ejectorreturn position;

FIG. 5 is a fragmentary sectional view of a portion of the same controlvalve taken on line V-V of FIG. 4 showing other details of the holdingmechanism; and

FIG. 6 is a fragmentary section taken on line VIVI of FIG. 3.

In FIG. 1, a conventional two-wheel scraper is illustrated at It) asdrawn by a tractor 11 through a hitch or draft connection generallyindicated at 12. The main body or bowl of the scraper may be raised andlowered about its pivotal connection with its wheels 13. Draft arms 14pivoted to opposite sides of the scraper bowl, as by connections one ofwhich is shown at 15, enable raising and lowering of the scraper bowl bymeans of a pair of jacks, one of which is shown at 16. A pivoted apron17 is adapted to be raised and lowered for opening and closing theforward end of the bowl by means of a jack 18, lever 18b and link 18c,and an ejector 19 is moved forwardly to discharge the contents of thebowl through its forward end by an ejector jack 20, all in. a well knownmanner. A control valve assembly 22 for controlling the flow of fluid toand from the several jacks is disposed on the tractor as are alsocontrol levers, one shown at 23, positioned adjacent the operatorsstation.

Generally speaking, the hydraulic circuits for operating the adjustableelements of the scraper are the same as those disclosed in our assigneesco-pending application entitled, Hydraulic Circuit for Tractor DrawnScrapers and the Like, filed November 24, 1961, Serial No. 154,790, nowPatent No. 3,115,716, and will be briefly described herein for thepurpose of showing the environment of the present invention.

The control valve assembly 22 is schematically shown in FIG. 2 ascomprising a single housing which is suitably bored for the reception ofthree sliding type valve spools 16a, 18a and 20a for controllingrespectively the jacks 16, 18 and 20. Each of the spools is formed atone end for connection to control levers and is fitted at its oppositeend with a centering spring assembly shown at 26, 28 and 30. Thefunction of such assemblies is well known and only that pertaining tothe ejector control is shown in detail to be hereinafter described,

A pump 35 delivers fluid under pressure from a reservoir 36 to an inletpassage 37 in the valve housing which is divided to direct fluidselectively toward either one end or the other of the valve spool 16adepending upon its position of adjustment. Similar inlet passages 38 and39 communicate with each other and with the first passage 37 so thatwith the valve spools in their neutral positions as shown, there is aconstant flow of fluid under pressure from the pump through the passages37, 38 and 39 and a discharge passage 40 and thence back to thereservoir through a return line 41. A relief valve 42 in the pressureline from the pump also has its discharge side connected with the returnline 41.

Each of the jacks or sets of jacks has what may be termed a highpressure and a low pressure end because the work of moving an implementpart in one direction, as when it is being raised or moving earth, isusually greater than that of moving it in the other direction. Movementof any one of the spools to the right connects it with the high pressureend of its associated jack. For example, the spool 16a upon movementtoward the right opens communication with the inlet chamber 37containing fluid under pressure from the pump and directs the fluid intoa line 46 to the rod ends of the jacks 16 for raising the bowl. Thefluid first passes through valves 16b associated with the jacks 16 in amanner and for a purpose fully disclosed in our assignees Patent No.

3,068,596, entitled, Hydraulic Circuit for Actuation of an EarthmovingScraper Bowl. Movement of spool 18a to the right similarly connects theinlet passage 38 thereof with a line 48 connecting with the head end ofthe jack 18 through a valve mechanism 64 described in the abovementioned patent. Upon movement of the spool 20a to the right, fluidunder pressure from inlet 3? thereof is directed through a line 50 tothe head end of the ejector jack 20. For convenience in following thesecircuits, the drawings identify the jacks as well as the spools with thepart of the implement with which they are associated.

The opposite or low pressure ends of the jacks are all connected with acommon manifold 52 which, as shown in'the' drawings, communicates witheach of the three" bores which contain the valve spools and is opened byrightward movement of any spool into communication with a dischargemanifold 53 also common to all three spools and communicating with therscrvoir through the line 41. Consequently when fluid is directed underpressure to the high pressure side of any of the jacks, fluid on the lowpressure side is returned to the reservoir. The common manifold 52 isconnected with the jacks through a common line 54 with a branch 55 tothe low pressure or head ends of the bowl jack 16, a branch 56 to therod end of the ejector jack 20 and a branch 57 to the rod end of theapron jack 18 through the valve mechanism 64.

Movement of the jacks in the direction opposite that described above isaccomplished by movement of any one of the valve spools in the oppositedirection or to the left which communicates high pressure through theactuated spool to the manifold 52 and thence to all of the jacks throughline 54 and its branches 55, 56 and 57. The valve spool which has beenactuated to the left also opens communication to a discharge passage 60which is common to all of the spools and similar to the dischargepassage 53. The discharge passage 60 permits return of fluid from thejack being actuated through the passage 4%) and line 41 to thereservoir. Under the condition just described where a single valve spoolis actuated and directs fluid to all three jacks, only the selected jackis moved because return flow from the other jacks is blocked by theirrespective spools which have remained in their neutral position. Thepresent invention provides means for causing the ejector circuit tooperate at either one of two speeds at the selection of the operator.This is accomplished by what will be termed a manual twospecd ejectorvalve generally illustrated at 65 in FIG. 2. The valve is shown in itshigh speed position wherein fluid under pressure through line 50 isacting upon the head end of the jack while fluid returning from the rodend of the jack through a line 66 is communicated, by reason of theconfiguration of a valve spool 67, to a line 68 which also communicateswith the head end of the jack. Thus the return fluid from the jack isadded to the fluid under pressure rather than returning to the reservoirand causes the jack to actuate at higher speed though with somewhatreduced force.

If the operator anticipates work in heavy or sticky material requiringgreater ejecting force, the position of the valve spool 67 is altered byactuation of a lever 70 having a cam 71 thereon to move the spool 67 inopposition to a spring 72 and thus block communication between the lines66 and 68 and establish communication between the lines 66 and 56 whichlatter is as previously described a return line for exhausting fluidfrom the rod end of the jack to the reservoir. In the high speedposition of the valve shown it is impossible to return the ejectorbecause the spool 67 is blocking communication between lines 56 and 66.Consequently a port 74 is provided in the spool to permit fluid underpressure in line 56 to enter a chamber 75 in which the cam 71 isdisposed and move the spool against action of the spring 7?. temporarilyto form a connection between lines 66 and 56 and admit fluid to the rodend of the jack for returning the ejector. Movement of the spool againstthe force of spring '72 either manually or by pressure in the chamber ispermitted by a bleed passage 76 which communicates with the springchamber to exhaust any fluid which may have leaked past the spool andbecome entrapped in the chamber. In order to prevent the same pressurewhich flows through passage 74 into chamber '75 from passing throughbleed passage 76 into the spring chamber and balancing the pressures onthe spool a small check valve 78 is disposed in a passage whichcommunicates between the bleed passage 76 and a side of the spool whichcommunicates with the line 68.

FIG. 3 shows a modification of of the two-speed valve 65 wherein thecontrol lever '70 is omitted and valve means are provided to effectchange of speeds automatically when the force required to move theejector changes. In FIG. 3, the valve 65a is similar in operation tothat shown at 65 in FIG. 2 and the same reference characters followed bythe letter a are employed to designate parts which are similar inconstruction and function. The valve spool 67a is normally urged to itslow speed position by a spring 72a now located at the upper end of thespool as viewed in FIG. 3 to provide communication between lines 66 and56 as described in connection with FIG. 2. It is desirable that spool67a be shifted to its high speed position upon introduction of fluidpressure to the head end of the ejector jack 2%) through the line 68. Inorder to accomplish this, pressure in line 68 is communicated through apassage 80 to the lower end of a reciprocable plunger 81, the oppositeend of which bears against the spool 67a to move it upward in oppositionto spring 72a. This is efiective to block communication between lines 66and 56 and direct displaced from the rod end of jack 26 to its head endto supplement the pump volume and provide high speed ejection.

In order to provide automatic two-speed ejection, it is necessary that ameans he provided to return spool 67a to its normal low speed positionwhen the pressure in line 68 exceeds a predetermined point. For thispurpose, a load responsive valve generally indicated at 82 is employedto selectively provide or interrupt communication of pressure to thechamber of spring 72a in response to loads which are reflected bypressure build-up in the head end of the jack and line 68. Pressure inthe line 68 is communicated through the valve 65a, in its high speedposition, through a passage 33 and connecting passages 84 and 85 in theload responsive valve to the end of a reciprocable plunger 86, theopposite end of which bears against a spool 87 held in the normalposition shown by a spring 83. During the ejection of sticky or heavymaterial tending to cause a build-up of pressure sufiicient to overcomethe force of the spring 86, the plunger 86 moves spool 87 to the rightas shown and high pressure in the passage 83 is communicated through apassage 89 to radial passages 96 in the spool 87, through an axialpassage 91 therein and other radial passages 92 to a passage X:communicating with the end of the spool 67a. Although the pressuresacting on the end of plunger 81 and directed to the upper end of spool6711 are equal, due to the area diiferential of these two surfaces andthe supplementing force of spring 72a, spool 67a is moved downward toits high force low speed position as described in connection to FIG. 2.Spool 67a will remain in this position until the force required foradvancing the ejector is reduced as for example, when the load is nearlydischarged from the bowl. At this time spring 68 returns the spool 87 tothe position shown. A return path for fluid contained at the end of thespool 67a while it is held in its high force position is provided by thepassage 93, radial passages 92, the axial bore 91 and other radialpassages 94, which communicate through passages 95 with the chamber ofspring 88 and thence through a passage 96 which communicates with theline 56. At this time the pressure acting on plunger 31 overcomes theforce of spring 72a to shift spool 67a to its high speed position.

When spool 67a is in a high speed position to interconnect the oppositeends of jack 20, the effective working area of its piston a is reducedto an area equal to the cross-sectional area of its piston rod 2%. Thisrequires a substantially higher pressure in the head end of the jackthan when the entire area of the left face of piston Zila (as viewed inFlG. 3) is etlective. For this reason it is desirable that a means beprovided to maintain spool 87 in the low speed position until pressurerequired to advance the ejector reduces an amount greater than thepressure change in the circuit due to a shift to the high speedcondition. In order to accomplish this as the pressure acting on plunger86 becomes great enough to overcome spring 88 and move spool 87 to theright as previously described, the pressure in passage 39 is alsodirected through an annular groove 87a in spool 87 and a radialclearance provided between a flange 875) on spool 87 and its cooperatingbore in the valve body to an area indicated 8% at the left end of thespool. Since the area of the end of spool 87 is substantially largerthan the area of plunger 86, spool 87 will be held in its low speedposition until the pressure in the head end of jack 2% has reduced theabove described amount. At this time the force of spring 88 willovercome the pressure in area 87c to return spool 87 to the high speedposition where it will be uninfluenced by the pressure increase in thecircuit due to the change in effective working area of piston Ala.

As spool 67a moves upward to block communication between lines 66 and 56and provides communication between lines 66 and 68, it is necessary toinsure that the fluid being displaced from the rod end of the jack isnever completely blocked to permit continuous movement of the ejector.For this purpose a land d7 of spool 67a is of such a size and positionedin relation to the port of line 66 in a manner such that at leastpartial communication is provided between lines 66 and 68 before thecommunication between lines 66 and 56 is completely blocked. Due to thefact, however, that relatively high pressure is present in line 6%, thispartial interconnection of the ports of lines 5 5, 66 and 6% permits asurge of pressure to flow from line 63 through the port of line 65 intoline 56 from where it is directed through passages 96 and 95, radialpassages 94 and axial passage 91. In order to prevent this pressuresurge from acting on the left end of spool 87 to return it to theposition providing communication between line 68 and a chamber of spring72a as previously described, a small check valve 98 is provided in axialpassage hi intermediate radial passages 90 and 92.

As spool 67:) shifts from the high speed to a low speed position due tothe sudden change in velocity of the ejector, there is the tendency forthe soil being ejected to momentarily leave the ejector, thus resultingin a substantial reduction in the pressure in the head end of the jackand line 68. This reduction in pressure permits spool 87 to return tothe position shown to communicate the chamber of spring 72:: with thereservoir 36 as previously described and permit spool 67b to return tothe high speed position. In order to prevent malfunction of the valveclue to this reduction in pressure, communication between lines 66 and56 through spool 67a is provided through a plurality of metering slots130 which are of a size to restrict the fluid returning to the reservoirfrom the rod end of jack 20. This maintains sufficient back pressure inthe rod end of the jack to prevent the excessive reduction in pressuredue to sudden change in the velocity of the ejector. This valve has ableed passage 76a and a check valve 73a functioning in the manner andfor the purpose of the passages 76 and valve 78 of FIG. 2.

It is necessary that spool 67b remain in its normal low speed positionwhen fluid is directed to the rod end of jack 20 to return the ejectorto its rearward position in the scraper bowl. For this purpose, a checkvalve 131 is located in passage 76a of spool 67a to prevent fluid underpressure in line 56 from entering the chamber below the spool 67a andmoving it to its high speed position to block communication betweenlines 56 and 66. In order to further insure that spool 67:: remains inits low speed position during this return movement of the ejector, thefluid pressure in line 56 is directed to the chamber of spring 72athrough passage 96 and load responsive valve 82.

Since communication between lines 56 and 66 is of a size to restrict thevolume of fluid displaced from the rod end of jack 28 during ejection ofmaterial contained in the bowl and the volume of fluid being directed tothe rod end of the jack through lines 56 and 66 is greater in volumethan the displaced fluid, the restriction in the valve 65a would createan excessive back pressure in line 56 thus resulting in wasted horsepower and heat generation in the hydraulic circuit. In order to provideunrestricted flow of fluid to the rod end of jack fill, a by-pass line132 is provided between the lines 56 and 66. A check valve It)? islocated in the by-pass line and is effective to permit free flow fromline 56 to line se and to block communication in the opposite directionso that fluid returning to the reservoir 36 must pass through therestriction of slots in spool 67a as previously described.

Another desirable feature of the present invention is that it providesmeans for holding the ejector control spool 20a in the ejector returnposition until the ejector completes its return stroke, thus freeing theoperator for attention to other controls. Referring first to FIG. 2 itwill be recalled that during the return stroke of the ejector fluid fromthe head end of jack 28 is being returned through line 50 under pressuretoward the reservoir. This pressure results from return movement of thepiston in jack 2t) and resistance created by transmission through thevarious conduits which return fluid to the reservoir. Part of thispressure is transmitted to the spring chamber of the centering springassembly 30 by means of a passage indicated in broken lines at 10%) inFIG. 2 and more clearly illustrated in FIG. 4 which is an enlargedsection taken through the center of this passage as viewed. at rightangles to FIG. 2. Fluid under pressure in passage 1th) opens a springpressed check valve 101 admitting fluid through a passage 102 in thevalve housing and a slot m3 in the spool to the spring chamber andmaintaining the spool in its leftward position which is that shown inFIG. 4. The pressure in the spring chamber of centering assembly 3%! isdesirably limited to a value which can be overcome by the operatorthrough manual control linkage in the event that he wishes to interruptreturn movement of the ejector. This is accomplished by a check valveassembly shown at 105 in FIG. 5 wherein a spring biased ball preventspassage of fluid from the spring chamber through passages 1% whichcommunicate with slots 167 in the spool 20m and through a passage 108 toa line 199 (see also FIG. 2) which leads to the reservoir. Thus if theoperator through manual controls urges the spool 20a toward its neutralposition with force sul'ficient to unseat the check valve (preferablyabout 65 psi.) the spool can be adjusted from its ejector returnposition of FIG. 4 to the neutral position of FIG. 5. If the returnmovement of the ejector is not interrupted by the operator the spool 20awill automatically return to its neutral position when the ejectorcompletes its travel. Since the piston of jack 20 reaches the end of itsstroke when the ejector is fully returned pressure in the line 5t) failsthus permitting the check valve 101 to close. As the centering spring inthe assembly 30 urges the spool toward its neutral position fluid in thespring chamber bleeds ofl, first through the slot 103, passage 102 and asmall orifice 111 in the check valve 101. Since the spool 20:: is movingtoward the right from the position of FIG. 4 the slot 103 is closedduring the initial movement. However, just before closing of the slot103 the slot 197 reg-istom with the spring chamber and permits continuedbleeding through orifices 112 in a spring seat 115 therein whichcommunicate fluid through slot 107 and passage 188 to the line 109communicating with the reservoir.

At the completion of the operation just described the centering springchamber remains filled with fluid which might produce a fluid lockpreventing the spool 20. 1 from moving toward the right which isnecessary to extend the jack 20 for ejecting material from the bowl.This fluid lock is relieved by a bleed port 114 normally closed by thespring seat in which the orifices 112 are formed. However, initialmovement of the spool 211a toward the right removes the spring seat 115from its position obstructing the bleed port 114 and relieving thehydraulic lock.

Holding the ejector spool in the return position as described abovedepends upon pressure created by return movement of the cylinder in theejector jack 21). Therefore should either of the spools 16a or 18a beactuated to adjust the position of the bowl jacks 16 or apron jack 18normal flow of pump pressure through area 39 (see FIG. 2) would, becausethe spools are in series, be interrupted cutting off pressure to theejector jack. Hence the piston of the ejector jack would stop, causingfailure of return pressure to line 56 and permitting spool 29a to returnto neutral position before the ejector has been fully returned. This isprevented by borrowing pressure from either of the spools 16a or 18a.which is actuated at this time. The means for accomplishing this isshown in FIGS. 2, 3 and 6 wherein conduits 116 and 117 are shown ascommunicating between the bores in which spools 16a and 18a slide and,through a junction box 119, with a conduit 12%) leading to the springchamber of check valve 101. Thus pressure is supplied through passage102 and slot 183 to the centering spring chamber to substitute for thepressure lost upon interruption of movement of the ejector jack. Themeans for communicating pressure from the spool bores to the lines 116and 117 is identical in both cases and is shown in FIG. 6 where thespool 18a is shown in its neutral position. A passage 122 communicatingwith conduit 117 is closed by the spool in this position. This passageis opened by movement of the spool toward the right when it is uncoveredby a land thereon. Upon movement to the left pressure is communicated tothe passage 122 first through passages 123 then through passages 124 andfinally through notches 125 formed in the edge of the land. The passages123 and 124 register with grooves 126 and 127 respectively whichcircumscribe the land and maintain its normal ability to seal while asmall portion of the pressure in the valve chamber is utilized asdescribed for holding the ejector valve spool 20a in its returnposition.

We claim:

In a hydraulic system including a jack having rod and head ends, a pump,and a control valve intermediate said pump and jack and including aspool valve operable manually to deliver r'iuid selectively to eitherend oi said jack, a second valve having a spool operable in response tohydraulic pressures, said second valve spool including a first positionto return fluid displaced from the rod end of the jack toward the pump,means carried by said second valve and operable in response to apredetermined reduction in pressure to move said spool to a secondposition to divert fluid displaced from the rod end of said jack to thehead end, preventive means associated with said last named means andoperable to prevent movement of said spool from said first to saidsecond positions until the pressure required to extend the jack hasreduced an amount greater than the pressure change in the systemresulting from moving from said first to said second positions, saidpreventive means including passages for admitting pressure from the jackto an end of the spool, and pressure responsive means to open and closesaid passages.

References Cited by the Examiner UNITED STATES PATENTS 2,367,682 6/1945Kehle 9l-436 2,619,118 11/1952 Adams 91 -436 2,890,683 6/1959 Pilch91436 2,976,878 3/1961 Smilges 91-436 FOREIGN PATENTS 212,519 8/1957Australia.

SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner. V

